Fished the Muchalet River on Vancouver Island with bears everywhere. Saw fresh tracks and started singing etc, feeling kind of foolish. I heard a curious "mewing" right alongside me in the thick brush along the bank, and kept on singing. Later, on the way out I came across a mama black bear and her two cubs coming out exactly where I'd heard the "mewing". I started clanking cans I'd found, and she tree'd the cubs.

Still get chills thinking how close we must have been.
Making a racket works.

But talking about protecting your cubs, I fished the Morice with a friend and his friend, a guide taking us on his busman's holiday for steelies. He brought along his two boys, about five and seven years old. A sow griz and her two cubs appeared upstream after we'd heard some roars. Being furthest downstream, I looked up in time to see the sow in the distance gather her cubs close by her, and in the foreground our guide with his two boys, one under each arm as he clambered to the jetboat. The sow and the guide united in a graceful get 'em up & go.

Whether man or beast, grab the cubs and run if warned; stand and fight if caught unawares. My experience is limited in bear country, but I'm a believer in making a racket.